We wanted to compare the analgesic efficacy and adverse effects of pharmacological treatments for acute migraine through a systematic review of randomised controlled trials in patients with acute migraine pain of moderate to severe intensity. Trials were identified from systematic searching of bibliographic databases. For eletriptan information from all trials was supplied by Pfizer Inc. Outcomes sought were headache relief at 1 and 2h, patients pain free at 2h and sustained relief over 24h for treatments compared with placebo. Numbers-needed-to-treat (NNTs) were calculated, together with relative benefit. Information on adverse effects was also collected. Comparisons of relative efficacy used the same definition of headache, the same degree of pain at the start of treatment and the same definitions of outcomes, and always compared with placebo. Forty-eight publications reporting on 54 trials were included in the meta-analyses, with 79 placebo comparisons for the primary outcome of headache relief at 2h. Information on any outcome was available for nine oral medications, two intranasal medications and subcutaneous sumatriptan in 21,022 patients. For headache relief at 2h NNTs ranged from 2.0 for subcutaneous sumatriptan 6mg to 5.4 for naratriptan 2.5mg. For patients pain free at 2h NNTs ranged from 2.1 for subcutaneous sumatriptan 6mg to 8.6 for aspirin 900mg plus metoclopramide 10mg. For sustained relief over 24h NNTs ranged from 2.8 for eletriptan 80mg to 8.3 for rizatriptan 5mg. It was not possible to systematically review adverse effects data. Most interventions are effective. There is considerable information on relative efficacy for a number of outcomes.